354 * PALEOZOIC PALEONTOLOGY. 
The dimensions of an imperfect brachial valve are, approximately: 
length, 44 mm.; width, 56 mm.; convexity, 20 mm. 
Remarks.—This very characteristic Oriskany species is one of the 
very rarest members of the fauna in New Jersey. It may always be 
easily recognized by its large size when adult and by its completely- 
plicated valves, it having no associates in the same genus which do 
not have a smooth fold and sinus. 
SPIRIFER MURCHISONI Castelnau. 
Plate XLVIII., Figs. 1-4. 
1859. Spwrtfer arrectus Hall, Pal. N. Y., vol. IIL., p. 422, pl: 97, figs. 
1 a—h, 2 a-. 
Description.—Shell semi-circular to semi-elliptical in outline, great- 
est width usually along the hinge-line; cardinal angles usually an- 
gular, rarely a little rounded, often somewhat mucronate. Pedicle 
valve gibbous on the umbo; the surface slightly flattened toward the 
cardinal angles, regularly curved to the front; mesial sinus sharply 
defined, subangular or rounded in the bottom; beak incurved; cardi- 
nal area high, sharply defined, concave toward the beak. Brachial 
valve strongly convex, more or less flattened toward the cardinal ex- 
tremities; the subangular fold usually greatly elevated towards the 
front. Surface of both valves marked by from five to eight simple, 
rounded or subangular plications on each lateral slope, the fold and 
sinus non-plicate. The surface also marked by fine, concentric, fim- 
briate lines and by stronger lines of growth. 
The dimensions of a rather large pedicle valve are, approximately: 
length, 34 mm.; width, 52 mm.; convexity, 16 mm. 
Remarks.—This is, perhaps, the commonest and most characteristic 
species in the Oriskany fauna of New Jersey. It is almost universal 
in its occurrence, but the specimens are never perfectly preserved and 
are frequently in the form of imperfect casts of the interior. In such 
specimens the brachial valve is usually not greatly different from the 
exterior of the shell, except in having somewhat stronger plications, 
but the pedicle valve is conspicuously marked by the cast of the large 
and deep muscular impression. 
